Diode rectifier bridges, such as that shown in FIG. 1, are well known from the prior art.
The diodes used in this type of rectifier bridges, whether these are junction, PIN or Schottky diodes, have a considerable voltage drop in the conducting direction at low voltage.
This represents a disadvantage in the field of motor vehicle equipment which runs at low voltage. For example, the electrical output of an alternator is degraded as a result.
To improve the overall output of the electrical equipment implementing diode bridges, it is known to use synchronous rectifiers having switches (transistors, thyristors, triacs, etc).
Document EP1347564 describes a three-phase synchronous rectifier bridge of this type, the schematic diagram of which is taken up in FIG. 2.
The gates of the transistors of the N-channel MOSFET (insulated gate field effect transistor) or IGBT (insulated gate bipolar transistor)-type which switch-operate are controlled according to the absolute value of the differences in voltages between phases so as to produce, at the output of the bridge, a continuous voltage.
It is also known from document WO2004/034439 to drive the MOSFETs in linear mode in the conducting state, i.e. to linearly drive their internal resistor by means of a servo-mechanism so as to simulate the behaviour of ideal diodes.
In document FR2884079, the company VALEO EQUIPEMENTS ELECTRIQUES MOTEUR discloses a method for controlling a MOS transistor, which is intended to be implemented in an electric converter bridge (inverter, or rectifier), for the purpose of overcoming the accumulation of electrical charges in the transistor which is responsible for the delay in switching, which produces a large recovery current. The schematic diagram of the corresponding device is given in FIG. 3.
The technical developments recalled above have lead to an optimisation of the output of synchronous rectifiers.
However, the transistors of known synchronous rectifiers require an additional control and supply circuit, and cannot replace a diode in order to transform an asynchronous rectifier bridge into a synchronous rectifier bridge.